Apparatus and method for transmission/reception

ABSTRACT

In a modulation method such as 8 PSK or a 16 PSK in which a sender device expresses a symbol by using three or more bits, important information is arranged at least at only one of the first and second bits, a receiver device extracts the important information from at least one of the first and second bits of the received signal, and thereby communication control is carried out based on the important information.

This is a continuation of application Ser. No. 09/582,558 filed Jun. 29,2000, the entire content of which is expressly incorporated by referenceherein.

TECHNICAL FIELD

The present invention relates to a transmission/reception apparatus, andin particular, to a transmission/reception apparatus for an OrthogonalFrequency Division Multiplexing system (hereinafter referred to as “OFDMtransmission/reception apparatus”).

BACKGROUND ART

A conventional OFDM transmission/reception apparatus is explained withreference to FIG. 1 below. FIG. 1 is a block diagram illustrating aconfiguration of a conventional OFDM transmission/reception apparatus.

In FIG. 1, parallel-serial converter (hereinafter referred to as “P/Sconverter”) 101 inserts important information into transmission data.This important information refers to a kind of information normalcommunication of which is likely to be difficult to be maintained if theother end of communication has a poor error rate characteristic duringreception. That is, the important information above is a kind ofinformation requiring a better-error rate characteristic than otherinformation (transmission data, for example).

An example of the important information above is retransmissioninformation or control information, etc. Retransmission informationrefers to information retransmitted to the other end of communicationaccording to a retransmission command issued by the other end ofcommunication. Control information refers to information used for theuser at the other end of communication to reliably receive anappropriate signal. Examples of control information can be informationindicating bursts in a communication frame to be received by the otherend of communication and information indicating the current modulationsystem during adaptive modulation, etc.

Serial-parallel converter (hereinafter referred to as “S/P converter”)102 converts the transmission signal, which is the output of P/Sconverter 101, to a plurality (here 4) of signals.

Mapping circuits 103 carry out primary modulation on the signals fromS/P converter 102 and send the primary-modulated signals to Inverse FastFourier Transform (hereinafter referred to as “IFFT”) circuit 104. IFFTcircuit 104 performs inverse Fourier transform processing on theprimary-modulated signals. D/A converter 105 converts the transmissionsignal, which is the output of IFFT circuit 104, to an analog signal.

On the other hand, A/D converter 106 converts a reception signal to adigital signal and sends it to Fast Fourier Transform (hereinafterreferred to as OFFTO) circuit 107. FFT circuit 107 performs Fouriertransform processing on the output signal of A/D converter 106.

Delay detectors 108 perform delay detection processing on thesubcarriers obtained by Fourier transform and determination circuits 109determine delay detection processing. P/S converter 110 converts aplurality of signals from determination circuits 109 to a single signaland S/P converter 111 extracts important information from the output ofP/S converter 110.

Then, the transmission/reception operations of the conventionalapparatus with such a configuration are explained.

After important information is inserted by P/S converter 101, thetransmission data is converted to a plurality of signals by S/Pconverter 102. The plurality of signals from S/P converter 102 aresubjected to primary modulation by mapping circuits 103. Theprimary-modulated signals are subjected to inverse Fourier transformprocessing by IFFT circuit 104. The signals subjected to inverse Fouriertransform processing by IFFT circuit 104 are converted to a digitalsignal by D/A converter 105 and transmitted.

The reception signal is converted to an analog signal by A/D converter106 and then subjected to Fourier transform processing by FFT circuit107. The signals carried by subcarriers after Fourier transformprocessing are subjected to delay detection processing by delaydetectors 108. The signals subjected to delay detection processing aredetermined by determination circuits 109 and sent to P/S converter 110.A plurality of signals from determination circuits 109 are converted toa single signal by P/S converter 110 and sent to S/P converter 111. S/Pconverter 111 extracts retransmission information and reception datafrom the single signal.

In this way, by the transmitter inserting important information into thetransmission signal, and the receiver extracting important informationfrom the reception signal and carrying out reception processing based onthe extracted important information, the receiver can receive the signaltransmitted by the transmitter correctly. This allows a smoothcommunication between the transmitter and receiver.

If retransmission information is taken as an example of importantinformation, by the transmitter inserting retransmission informationinto the transmission signal and the receiver extracting theretransmission information from the reception signal, the receiver cansend an appropriate retransmission command to the transmitter. That is,the receiver can send back a signal with information carried on acontrol channel indicating which cell of which burst had an error.

However, the conventional apparatus has problems as shown below. Thatis, in the conventional apparatus, as the transmission efficiency isimproved, the channel quality deteriorates, and the more thetransmission efficiency is improved, the higher the probability that thereceiver will not correctly receive the signal (for example, importantinformation and transmission data) sent by the transmitter is. That is,the higher the transmission efficiency, the worse the error ratecharacteristic of important information in the receiver. As a result, itwill be difficult for the receiver to maintain correct reception and itwill be difficult to maintain a normal communication between thetransmitter and receiver as a whole.

Here, suppose the modulation system is changed from QPSK to 8 PSK toimprove the transmission efficiency.

In 8 PSK, one symbol is expressed with 3 bits. As shown in FIG. 2, inthe 1st bit, “0” and “1” are switched round every 180 degrees on an I-Qplane; in the 2nd bit, “0” and “1” are switched round every 90 degreeson the I-Q plane; and in the 3rd bit, “0” and “1” are switched roundevery 45 degrees on the I-Q plane. That is, every time the number ofbits increases, the phase likelihood becomes half the phase likelihoodof the preceding bit. Therefore, the phase likelihood of the 3rd bitbecomes half the QPSK phase likelihood, and thus errors occur mostfrequently in the 3rd bit.

Here, when retransmission information is used as important informationif the error rate characteristic of retransmission information in thereceiver deteriorates as described above, the transmitter retransmitsthis retransmission information more frequently, which makes longer thetime until the communication is completed. Normally, there is a limit tothe number of retransmission times of certain information and ifretransmission is not completed within this limit, error correction isnot carried out for this information. This makes it impossible tomaintain a normal communication when carrying out a communication, whichrequires an optimal error characteristic such as image communication.

Moreover, when information indicating the current modulation system isused as important information, if the error rate characteristic of thisinformation deteriorates on the receiving side, it is difficult for thereceiving side to recognize the modulation system used by thetransmitting side, making it impossible for the receiver to receive thesignal transmitted by the transmitter. This makes it impossible tomaintain a normal communication between the transmitting side andreceiving side.

DISCLOSURE OF INVENTION

The present invention has been implemented taking account of thesituations described above and it is an objective of the presentinvention to provide a transmission/reception apparatus that willimprove the transmission efficiency while maintaining the transmissionquality of important information.

This objective is achieved in a modulation system that expresses 1symbol of 8 PSK or 16 PSK, etc. using 3 or more bits by placinginformation selected from all information to be communicated on at leastone of the 1st bit or 2nd bit only.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of a conventional OFDMtransmission/reception apparatus;

FIG. 2 is a schematic diagram showing an I-Q plane when 8 PSK modulationis used in the conventional OFDM transmission/reception apparatus;

FIG. 3 is a block diagram showing a configuration of atransmission/reception apparatus according to an embodiment of thepresent invention;

FIG. 4 is a schematic diagram showing a layout of important informationaccording to the conventional transmission/reception apparatus; and

FIG. 5 is a schematic diagram showing a layout of important informationof the transmission/reception apparatus according to the embodiment ofthe present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment

With reference now to the attached drawings, an embodiment of thepresent invention is explained in detail below.

The transmission/reception apparatus according to an embodiment of thepresent invention places important information on at least one of the1st bit or 2nd bit only in an OFDM-based radio communication that uses 8PSK as the modulation system and 4 carriers for transmission.

The transmission/reception apparatus according to the present embodimentis explained with reference to FIG. 3 to FIG. 5 below. FIG. 3 is a blockdiagram showing a configuration of the transmission/reception apparatusaccording to the embodiment of the present invention. FIG. 4 is aschematic diagram showing a layout of important information of theconventional transmission/reception apparatus using 8 PSK modulation.FIG. 5 is a schematic diagram showing a layout of important informationof the transmission/reception apparatus according to the embodiment ofthe present invention.

In FIG. 3, important information is converted to a plurality (here 4) ofsignals by S/P converter 301. Transmission data is converted to aplurality (here 4) of signals by S/P converter 302.

Here, important information refers to a kind of information normalcommunication of which is likely to be difficult to be maintained if theother end of communication has a poor error rate characteristic duringreception. Examples of the important information above can beretransmission information or control information. Examples of controlinformation can be information indicating bursts in a communicationframe that the other end of communication should receive, informationindicating the current modulation system during adaptive modulation,information that the other end of communication uses to distinguish asignal from the transmission/reception apparatus according to thepresent embodiment from other interference signals and informationindicating which burst in a frame the other end of communication willreceive.

Here, S/P converter 301 places important information on at least one ofthe 1st or 2nd bit only. Here, suppose the important information isplaced on the 1st bit only. This placement will be described in detaillater.

The important information and transmission data are primary-modulated bymapping circuits 303 and then subjected to inverse Fourier transformprocessing by IFFT circuit 304. The transmission data subjected toinverse Fourier transform are converted to an analog signal by D/Aconverter 305. This transmission signal is subjected to predeterminedradio transmission processing and then transmitted via an antenna.

On the other hand, a signal received via an antenna is subjected topredetermined radio reception processing and converted to a digitalsignal by A/D converter 306 and sent to FFT circuit 307. FFT circuit 307performs Fourier transform processing on the digital-converted receptionsignal. This allows a signal carried by each subcarrier to be extracted.Signals carried by the subcarriers are subjected to delay detectionprocessing by delay detectors 308. The signals carried by thesubcarriers and subjected to delay detection processing are determinedby determination circuits 309. Determination circuits 309 output thereception signal by separating the 1st bit from other bits (that is, 2ndbit and 3rd bit) in the reception signal.

The 1st bits of the reception signal are sent to P/S converter 310 andconverted to a single signal. In this way, retransmission information isobtained from P/S converter 310 as reception data. On the other hand,the 2nd bits and 3rd bits of the reception signal are sent to P/Sconverter 311 and converted to a single signal. Thus, the reception dataare obtained from P/S converter 311.

Here, the method of placing important information is explained withreference to FIG. 4 and FIG. 5. FIG. 4 shows a case in the prior artwhere important information is placed on all bits at a certain time onthe time axis and FIG. 5 shows a case where important information isplaced on the 1st bit only. In the present embodiment, transmission isperformed with important information placed on the 1st bit only as shownin FIG. 5.

In the case of 8 PSK, one symbol is expressed with 3 bits as shown inFIG. 2. As is clear from FIG. 2, in the 1st bit, “0” and “1” areswitched round every 180 degrees on an I-Q plane; in the 2nd bit, “0”and “1” are switched round every 90 degrees on the I-Q plane; and in the3rd bit, “0” and “1” are switched round every 45 degrees on the I-Qplane. That is, every time the number of bits increases, the phaselikelihood becomes half the phase likelihood of the preceding bit.

Therefore, in the case of 8 PSK, the phase likelihood successivelydecreases on the 1st bit, 2nd bit and 3rd bit. The phase likelihood ofthe 2nd bit is equivalent to the phase likelihood of QPSK. Therefore, asshown in FIG. 5, placing important information only on the 1st bitallows important information to be sent with high quality.

Here, communication control based on important information is explainedwith reference to FIG. 3 again. Here, communication control is explainedfor two cases, when retransmission information is used as importantinformation and when control information is used as importantinformation. By way of example, a case where a 1st communicationapparatus and 2nd communication apparatus equipped with thetransmission/reception apparatus shown in FIG. 3 perform a radiocommunication is explained.

First, communication control when retransmission information is used asimportant information is explained. The 1st communication apparatusextracts important information and reception data by carrying out theprocessing described above on the reception signal. The extractedimportant information and reception data are subjected to errordetection processing.

Of the important information or reception data, the data from which someerror has been detected by the error detection processing above are sentto a retransmission instruction section (not shown in the figure). Theretransmission instruction section creates retransmission information torequest retransmission of the data from which the error has beendetected. That is, the retransmission instruction section instructsretransmission as communication control.

The retransmission information created by this retransmission controlsection is input to S/P section 301 as important information. Thetransmission data containing this important information are subjected tothe processing above to become a transmission signal. This transmissionsignal is sent to the 2nd communication apparatus.

On the other hand, the 2nd communication apparatus extracts importantinformation and reception data by carrying out the processing above onthe reception signal. The extracted important information and receptiondata are subjected to error detection processing. The importantinformation contains retransmission information that the 1stcommunication apparatus requests for retransmission of predetermineddata. This important information is sent to a retransmission instructionsection (not shown in the figure). The transmission data containing thisimportant information is subjected to the processing above to become atransmission signal. This transmission signal is sent to the 1stcommunication apparatus.

Furthermore, the 1st communication apparatus extracts importantinformation and reception data from the reception signal in like manner.This important information and reception data are subjected to errordetection processing likewise. Since the important information is sentplaced on the 1st bit by the 2nd communication apparatus, the importantinformation becomes a signal with an optimal error rate characteristic.That is, the retransmission information resent by the 2nd communicationapparatus as important information is extracted by the 1st communicationapparatus without any error.

As shown above, even if the reception data in the 1st communicationapparatus contains some error, the 1st communication apparatus sendsretransmission information requesting for retransmission of the data inwhich the error occurred as important information to the 2ndcommunication apparatus. Since the 2nd communication apparatus canreceive important information without errors, it can recognize theretransmission request of the 1st communication apparatus correctly.

Furthermore, the 2nd communication apparatus sends the dataretransmission of which was requested by the 1st communication to the1st communication apparatus as important information, and thus the 1stcommunication apparatus can receive this important informationcorrectly. Thus, the 1st communication apparatus can suppress thefrequency of issuing a retransmission request again for the dataretransmission of which was requested once. As a result, a normalcommunication is maintained favorably between the 1st and 2ndcommunication apparatuses.

Then, communication control when control information is used asimportant information is explained. In the 1st communication apparatus,various control information is input to S/P section 301 as importantinformation. As the various control information, information indicatingbursts in a communication frame to be received by the 2nd communicationapparatus, information indicating the current modulation system, orinformation used for the 2nd communication apparatus to identify thesignal sent from the 1st communication apparatus from among otherinterference signals, etc. is used. The important information above andtransmission data are subjected to the processing above to become atransmission signal. This transmission signal is sent to the 2ndcommunication apparatus.

On the other hand, the 2nd communication apparatus extracts importantinformation and reception data from the reception signal by carrying outthe processing above. The important information, that is, variouscontrol information is sent placed on the 1st bit by the 1stcommunication apparatus, and therefore is a signal with an optimal errorrate characteristic. The extracted various control information is sentto a reception control section (not shown in the figure).

The reception control section performs reception control ascommunication control based on the extracted various controlinformation. For example, if information indicating bursts to bereceived by the 2nd communication apparatus is used in the communicationframe as various control information, the reception control sectionsends a control signal instructing that processing should be onlyperformed on the bursts shown in the information above to each sectionshown in FIG. 3. Furthermore, if information indicating the currentmodulation system is used as various control information, the receptioncontrol section sends a control signal instructing that a demodulationsystem corresponding to the modulation system indicated by theinformation above should be used to delay detectors 308.

As shown above, the 1st communication apparatus sends various controlinformation to the 2nd communication apparatus as important informationand the 2nd communication apparatus can receive this various controlinformation without errors, thus enabling correct reception processingaccording to the instruction from the 1st communication apparatus. As aresult, a normal communication is maintained favorably between the 1stand 2nd communication apparatuses.

Here, the case where the 1st communication apparatus sends variouscontrol information to the 2nd communication apparatus as importantinformation is explained, but it goes without saying that the 2ndcommunication apparatus can also send various control information to the1st communication apparatus as important information.

As shown above, even if errors occur relatively more frequently on the3rd bit, placing important information on the 1st bit prevents thequality of important information from being affected. As a result, thepresent embodiment allows the quality of important information even in 8PSK transmission to be maintained the same as that in QPSK transmission.This allows a normal communication to be maintained between thetransmitter and receiver.

For example, if retransmission information is used as importantinformation, the transmitter places retransmission information on the1st bit, and thus the receiver can maintain the error ratecharacteristic of retransmission information in an optimal condition.This can reduce the number of times the transmitter resendsretransmission information, making it possible to maintain a normalcommunication even when carrying out communication requiring anextremely high error rate characteristic such as an image communication.

Furthermore, if information indicating the current modulation system isused as important information, the transmitter places this informationon the 1st bit, and thus the receiver can maintain the error ratecharacteristic of this information favorably. This allows the receiverto receive the signal sent by the transmitter correctly by using ademodulation system corresponding to the modulation system used by thetransmitter. As a result, a normal communication can be maintained evenin the case where the adaptive modulation method is used.

The present embodiment explains the case where important information isplaced on the 1st bit, but if important information is placed on any bitother than the 3rd bit, which is more susceptible to errors, forexample, the 2nd bit, the quality of important information can bemaintained at a level at least equivalent to that in QPSK transmission.

Furthermore, the present embodiment explains the case where importantinformation is used as the information to be placed on the 1st bit or2nd bit. However, the present invention is not limited to this, but isalso applicable to a case where information other than importantinformation is used as the information to be placed on the above bits.That is, the information to be placed on the 1st bit or 2nd bit can beselected from among all information to be sent (all information to becommunicated) according to various conditions such as the level ofimportance.

It goes without saying that the present invention is applicable not onlyto a case where only one piece of information is always used as theinformation to be placed on the above bits but also to a case where theinformation to be placed on the above bits is changed at any timeaccording to various conditions.

Furthermore, the present embodiment explains the case where 8 PSK isused, but the present invention is also applicable to a modulationsystem in which one symbol is expressed with 3 or more bits, forexample, 16 PSK, 32 PSK. etc., in like manner.

Furthermore, the present embodiment explains the case with an OFDM-basedcommunication, but the present invention is applicable regardless of thecommunication system.

The transmission/reception apparatus of the present invention has aconfiguration comprising a modulator for modulating in such a way thatone symbol is expressed using 3 or more bits and a placer for placinginformation selected from all information to be communicated on at leastone of the first bit or second bit of a transmission signal.

Even with a modulation system such as 8 PSK in which one symbol isexpressed using 3 or more bits, the present invention is capable oftransmitting information selected from information to be communicated(for example, retransmission information, important information andtransmission data, etc.) with the quality equivalent to that in the caseof using a QPSK modulation system in which one symbol is expressed with2 bits, making it possible to improve the transmission rate of radiocommunication and maintain the quality of the information selected aboveas well.

The transmission/reception apparatus of the present invention has aconfiguration in which the information is selected from all informationto be communicated according to the level of importance.

The present invention can use information selected according to thelevel of importance (for example, information requiring an optimal errorrate to maintain a normal communication) as the information to maintainoptimal the error rate characteristic during reception, thus making itpossible to maintain a normal communication even if the channel qualitydeteriorates for the purpose of improving the transmission efficiency.

The transmission/reception apparatus of the present invention has aconfiguration comprising an extractor for extracting information from atleast one of the 1st bit or 2nd bit of a reception signal modulated Caccording to a modulation system in which one symbol is expressed using3 or more bits and a communication controller for performingcommunication control based on the extracted information.

Even with a modulation system such as 8 PSK in which one symbol isexpressed using 3 or more bits, the present invention can extractinformation from the reception signal with the quality equivalent tothat in the case of using a QPSK modulation system in which one symbolis expressed with 2 bits and perform communication control based on theextracted information, making it possible to maintain a normalcommunication.

The transmission/reception apparatus of the present invention has aconfiguration in which the information is selected from all informationto be communicated according to the level of importance.

The present invention can perform communication control based on theinformation selected according to the level of importance (for example,information requiring an optimal error rate to maintain a normalcommunication, etc.), making it possible to maintain a normalcommunication even in a case where the channel quality deteriorates forthe purpose of improving the transmission rate.

The transmission/reception apparatus of the present invention has aconfiguration with the communication controller comprising aretransmission instructor for instructing the other end of communicationto retransmit based on the information.

The present invention instructs the other end of communication toretransmit using retransmission information placed on the 1st or 2nd bitof the reception signal even in a case where the channel qualitydeteriorates for the purpose of improving the transmission rate, makingit possible to maintain a normal communication.

The transmission/reception apparatus of the present invention has aconfiguration with the communication controller comprising a receptioncontroller for performing reception control on the reception signalbased on the information.

The present invention performs reception control using informationplaced on the 1st or 2nd bit of the reception signal even in a casewhere the channel quality deteriorates for the purpose of improving thetransmission rate, making it possible to receive the reception signalcorrectly. This allows a normal communication to be maintained.

The base station apparatus according to the present invention isequipped with a transmission/reception apparatus comprising a modulatorfor modulating in such a way that one symbol is expressed using 3 ormore bits and a placer for placing information selected from allinformation to be communicated on at least one of the 1st bit or 2nd bitof a transmission signal.

Even with a modulation system such as 8 PSK in which one symbol isexpressed using 3 or more bits, the present invention is capable oftransmitting information with the quality equivalent to that in the caseof using a QPSK modulation system in which one symbol is expressed with2 bits, making it possible to improve the transmission rate of radiocommunication and maintain the quality of the retransmission informationas well.

The communication terminal apparatus of the present invention isequipped with a transmission/reception apparatus comprising a modulatorfor modulating in such a way that one symbol is expressed using 3 ormore bits and a placer for placing information selected from allinformation to be communicated on at least one of the 1st bit or 2nd bitof a transmission signal.

Even with a modulation system such as 8 PSK in which one symbol isexpressed using 3 or more bits, the present invention is capable oftransmitting information with the quality equivalent to that in the caseof using a QPSK modulation system in which one symbol is expressed with2 bits, making it possible to improve the transmission rate of radiocommunication and maintain the quality of the retransmission informationas well.

The base station apparatus according to the present invention has aconfiguration comprising an extractor for extracting retransmissioninformation from at least one of the 1st bit or 2nd bit of a receptionsignal modulated according to a modulation system in which one symbol isexpressed using 3 or more bits and a retransmission instructor forinstructing a radio station, which is the transmission source, toretransmit based on the extracted retransmission information using acontrol channel.

Even with a modulation system such as 8 PSK in which one symbol isexpressed using 3 or more bits, the present invention is capable ofextracting retransmission information with the quality equivalent tothat in the case of using a QPSK modulation system in which one symbolis expressed with 2 bits, making it possible to eliminate the need toinstruct for the third time, for example, a mobile station which is theradio communication destination, to retransmit, reducing communicationload on the other end of communication.

The communication terminal apparatus according to the present inventionhas a configuration comprising an extractor for extractingretransmission information from at least one of the 1st bit or 2nd bitof a reception signal modulated according to a modulation system inwhich one symbol is expressed using 3 or more bits and a retransmissioninstructor for instructing a radio station, which is the transmissionsource, to retransmit based on the extracted retransmission informationusing a control channel.

Even with a modulation system such as 8 PSK in which one symbol isexpressed using 3 or more bits, the present invention is capable ofextracting retransmission information with the quality equivalent tothat in the case of using a QPSK modulation system in which one symbolis expressed with 2 bits, making it possible to eliminate the need toinstruct for the third time, for example, a base station, which is theradio communication destination, to retransmit, reducing communicationload on the other end of communication.

The transmission/reception method of the present invention comprises amodulating step of modulating in such a way that one symbol is expressedusing 3 or more bits and a placing step of placing information selectedfrom all information to be communicated on at least one of the 1st bitor 2nd bit of a transmission signal.

Even with a modulation system such as 8 PSK in which one symbol isexpressed using 3 or more bits, the present invention is capable oftransmitting information selected from information to be communicated(for example, retransmission information, important information andtransmission data, etc.) with the quality equivalent to that in the caseof using a QPSK modulation system in which one symbol is expressed with2 bits, making it possible to improve the transmission rate of radiocommunication and maintain the quality of the information selected aboveas well.

The transmission/reception method of the present invention comprises anextracting step of extracting information from at least one of the 1stbit or 2nd bit of a reception signal modulated according to a modulationsystem in which one symbol is expressed using 3 or more bits and acommunication control step of performing communication control based onthe extracted information.

Even with a modulation system such as 8 PSK in which one symbol isexpressed using 3 or more bits, the present invention can extractinformation from the reception signal with the quality equivalent tothat in the case of using a QPSK modulation system in which one symbolis expressed with 2 bits and perform communication control based on theextracted information, making it possible to maintain a normalcommunication.

As described above, in a modulation system such as 8 PSK and 16 PSK inwhich one symbol is expressed using 3 or more bits, thetransmission/reception apparatus of the present invention placesinformation selected from all information to be communicated on at leastone of the 1st bit or 2nd bit only, making it possible to improve thetransmission efficiency while maintaining the transmission quality ofimportant information.

This application is based on the Japanese Patent Application No. HEI10-316417 filed on Nov. 6, 1998 and the Japanese Patent Application No.HEI 11-220827 filed on Aug. 4, 1999, entire content of which isexpressly incorporated by reference herein.

INDUSTRIAL APPLICABILITY

The present invention is ideally suited to the field of atransmission/reception apparatus for an orthogonal frequency divisionmultiplexing system.

1. A transmission apparatus comprising: a converting section that hasinput thereto through different routes a first information sequencecomprising a plurality of bits and a second information sequencecomprising a plurality of bits and that generates a sequence of bitsincluding at least one bit of the first information sequence and atleast one bit of the second information sequence; and a modulationsection that modulates the sequence of bits such that each of symbols isexpressed using three or more bits, wherein the first bits and thesecond bits of the symbols are comprised of the bits corresponding tothe first information sequence and the bits corresponding to the secondinformation sequence, and the more lower bits than the second bits ofthe symbols are comprised of bits corresponding to the secondinformation sequence.
 2. The transmission apparatus according to claim1, wherein the bits corresponding to the first information sequence arearranged on the first bits of the symbols.
 3. The transmission apparatusaccording to claim 1, wherein the bits corresponding to the firstinformation sequence are arranged on the first bit and the second bit ofat least one of the symbols.
 4. The transmission apparatus according toclaim 1, wherein the bit corresponding to the second informationsequence is arranged on the second bit of at least one of the symbols.5. The transmission apparatus according to claim 1, wherein the firstinformation sequence is separated from all information to betransmitted.
 6. The transmission apparatus according to claim 1, whereinthe first information sequence is one of retransmission information andcontrolling information.
 7. The transmission apparatus according toclaim 1, wherein the first information sequence is used for an errorcontrol.
 8. A base station apparatus comprising the transmissionapparatus according to claim
 1. 9. A communication terminal apparatuscomprising the transmission apparatus according to claim
 1. 10. Atransmission method comprising: inputting a first information sequencecomprising a plurality of bits and a second information sequencecomprising a plurality of bits through different routes; generating asequence of bits including at least one bit of the first informationsequence and at least one bit of the second information sequence; andmodulating the sequence of bits such that each of the symbols isexpressed using three or more bits, wherein the first bits and thesecond bits of the symbols are comprised of the bits corresponding tothe first information sequence and the bits corresponding to the secondinformation sequence, and the more lower bits than the second bits ofthe symbols are comprised of bits corresponding to the secondinformation sequence.
 11. The transmission method according to claim 10,wherein the bits corresponding to the first information sequence arearranged on the first bits of the symbols.
 12. The transmission methodaccording to claim 10, wherein the bits corresponding to the firstinformation sequence are arranged on the first bit and the second bit ofat least one of the symbols.
 13. The transmission method according toclaim 10, wherein the bit corresponding to the second informationsequence is arranged on the second bit of at least one of the symbols.14. The transmission method according to claim 10, wherein the firstinformation sequence is one of a retransmission information and acontrolling information.
 15. The transmission method according to claim10, wherein the first information sequence is used for an error control.16. A reception apparatus comprising: a receiving section that receivesthe sequence of bits including at least one bit of the first informationsequence and at least one bit of the second information sequencetransmitted by the transmission apparatus according to claim
 1. 17. Areception apparatus comprising: a receiving section that receives asequence of bits including at least one bit of a first informationsequence and at least one bit of a second information sequence, thesequence of bits being modulated such that each of the symbols isexpressed using three or more bits, wherein the first bits and thesecond bits of the symbols are comprised of the bits corresponding tothe first information sequence and the bits corresponding to the secondinformation sequence, and the more lower bits than the second bits ofthe symbols are comprised of bits corresponding to the secondinformation sequence; and a demodulating section that demodulates thesequence of bits, wherein the demodulating section extracts the bitscorresponding to the first information sequence from at least one of thefirst bits and the second bits of the symbols and extracts the bitscorresponding to the second information sequence from both of (i) atleast one of the first bits and the second bits and (ii) the more lowerbits than the second bits of the symbols.
 18. The reception apparatusaccording to claim 17, wherein the bits corresponding to the firstinformation sequence are arranged on the first bits of the symbols. 19.A base station apparatus comprising the reception apparatus according toclaim
 17. 20. A communication terminal apparatus comprising thereception apparatus according to claim 17.